One method to operate randomly operable valves in an internal combustion engine is described in U.S. Pat. No. 7,066,121. This method describes two intake valves of a cylinder are alternatively actuated, or opened, during different cylinder cycles of the cylinder (a cylinder cycle is defined herein as the period in crank angle duration wherein a operation of a cylinder repeats; e.g., in the case of a four-stroke cylinder cycle a cylinder cycle is 720 crankshaft angle degrees, but note that a cylinder cycle may increase or decrease depending on the number of strokes per cylinder cycle). That is, the first of two intake valves is held closed while the second intake valve opens during a cylinder cycle. Then, during the following cylinder cycle, the second valve remains closed while the first intake valve opens. In this way, opening events for the first and second intake valves are alternated every other cylinder cycle. This mode of operation may reduce power consumption and improve the cylinder air amount control.
The above-mentioned method can also have several disadvantages. For example, cylinder breathing characteristics may change depending on the valve that is operated during a particular cylinder cycle. That is, the cylinder may intake more air or less air when one valve is operated as compared to the other valve. This can cause engine air-fuel variation and engine torque variation, at least in some conditions.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of improving alternating intake valve control that offers substantial improvements.